EEG Coherence Effects of Audio-Visual Stimulation (AVS) at Dominant and Twice Dominant Alpha Frequency

Resumo

The effects of a single session of audio-visual stimulation (AVS) at the dominant alpha rhythm and twice-dominant alpha frequency on EEG coherence were studied in 23 subjects. An eyes-closed baseline EEG determined each subject’s dominant alpha frequency. Subjects were stimulated at their dominant alpha frequency or at their twice dominant alpha frequency for 20 minutes, while EEG was recorded in five-minute intervals. A post-session baseline was recorded 30 minutes after each session. AVS decreased coherence in the intrahemispheric projections from the occipital region and the parietal midline, and generally increased coherence, with few exceptions, among all other longitudinal pairs. Interhemispheric coherence increased posteriorly and at high frequencies, and tended to decrease frontally and at low frequencies. Alpha AVS was more effective than twice-alpha AVS at increasing interhemispheric coherence, and tended to produce more effects overall. Although main effects of frequency and time were observed, when individual coherence pairs changed, they almost always changed in only one direction. Overall coherence was greater during the first 10 minutes than the last 10 minutes, and greatest in the beta 1 and delta 2 bands, and lowest in the alpha and delta 1 bands. Few, if any, significant effects persisted into the post-stimulation baseline. A new method of assessing the effects of multiple comparisons on experimentwise error, based on randomization theory, is proposed and implemented.